As shown in FIGS. 1 and 2, a general sliding apparatus is provided in which a sliding member 22 having a substantially inverted U-shaped cross section and having arm portions 22c on the right and left sides of a base portion 22b is fitted on a shaft 21 provided on a base member 29, the sliding member 22 is adapted to be slidable reciprocatingly relative to the shaft 21, a loading path 23 composed of first loading grooves 21a provided on both sides of the shaft 21 and second loading grooves 22a provided, respectively, on inner surfaces of right and left arm portions 22c of the sliding member 22 and confronted with the first loading grooves 21a is provided between the shaft 21 and the sliding member 22, and a plurality of rolling members 24 are arranged at a predetermined interval in the loading path 23 so that the rolling members 24 may be rolled and moved in accordance with the sliding movement of the sliding member 22. Incidentally, in the drawings, reference numeral 26 denotes first loading portion forming member provided on the shaft 21 and reference numeral 27 denotes second loading portion forming member provided on the sliding member 22.
By the way, as described above, the sliding member 22 is slidingly moved relative to the shaft 21 together with the rolling movement of the rolling members 24. However, since when the rolling members 24 collide against each other upon rolling movement, this causes the hindrance of the smooth sliding movement of the sliding member 22 or the generation of noises, rolling member retainers 25 in which rolling member aligning windows 25a are formed in a plate member are arranged in the above-described loading path 23 and the rolling members 24 are arranged in the rolling member aligning windows 25a of the rolling member retainers 25 as shown in FIG. 2, whereby the interval between the adjacent rolling members 24 may be kept constant and the collision of the adjacent rolling members 24 may be prevented.
On the other hand, it is known that, in the conventional sliding apparatus, a phenomenon that a relative position among the shaft 21, the sliding member 22 and the rolling member retainers 25 is gradually displaced in accordance with the reciprocating sliding movement of the sliding member 22, i.e., a so-called “micro slip” phenomenon would occur.
The displacement of the rolling member retainers 25 due to the micro slip phenomenon causes the friction between the rolling member retainers 25 and the rolling members 24. This friction prevents the smooth movement of the sliding members 22 or causes the noises. Furthermore, when the displacement becomes remarkable, the rolling member retainers 25 would be broken to cause a serious damage to the instrument into which the sliding apparatus is incorporated.
Therefore, in order to prevent the above-described micro slip phenomenon, for example, as in Japanese Patent Application Laid-Open No. Hei 11-315831 (hereinafter referred to as Patent Publication 1) as shown in FIGS. 3 and 4 and as in Japanese Patent Application Laid-Open No. Hei 11-315832 (hereinafter referred to as Patent Publication 2) as shown in FIGS. 5 and 6, a disc member 32 having a plurality of convex portions 30 is coupled with a rolling member retainer 25, a plurality of concave portions 31 in concave and convex engagement with the convex portions 30 of the disc member 32 are provided in a loading path 23, the convex and concave engagement mechanism composed of the convex portions 30 and the concave portions 31 is caused to work so that the rolling member retainer 25 is moved along the loading path 23, whereby the above-described displacement of the rolling member retainer 25 may be prevented. However, this is complicated in structure and inferior in durability and worse in maintenance property and it is inevitable to increase the cost.
More specifically, Patent Publications 1 and 2 are directed to the structure where the disc member 32 which is discrete from the rolling members 24 to be coupled with the rolling member retainer 25 is provided in a central portion of the rolling member retainer 25. Since this disc member 32 is not subjected to any load from the loading path 23, the convex and concave engagement relationship of the convex and concave engagement mechanism is loose (that is, the convex and concave engagement is not firmly attained). Thus, it is impossible to completely prevent the micro slip phenomenon.
Also, since the disc member 32 is large in size relative to the rolling members 24, an effective stroke length of the sliding member is short. If this effective stroke length is to be elongated, it is necessary to shorten the length of the rolling member retainer 25 correspondingly, so that the rolling members 24 retained by the rolling member retainer 25 are reduced to cause a problem that the loading capacity is reduced.
Furthermore, since the disc member 32 is adapted to be coupled with the rolling member retainer 25, it is necessary to provide a shaft 33 for pivotally retaining the disc member 32. Since this is usually made of resin, the machining thereof is troublesome in precision and rigidity.
Patent Publication 1: Japanese Patent Application Laid-Open No. Hei 11-315831
Patent Publication 2: Japanese Patent Application Laid-Open No. Hei 11-315832